Sportsmen such as fishermen, migrant waterfowl hunters, etc. customarily use rubber waders to obtain access to stream beds too deep for conventional rubber overshoe products. These rubber waders are commercially available in a variety of forms such as hip or waist waders. Hip waders typically comprise two separate rubber vulcanizate boots, each fitted with an upper extending to the wearer's hip. Waist waders are typically of unitary construction similar in design to ordinary trousers. Other wader versions extend upwardly from the waist to cover the chest or shoulder regions of the wearer.
Waders of a rubber vulcanizate construction are particularly well suited for this purpose. The rubber construction provides a protective outerwear substantially impervious to water penetration. The rubber vulcanizate has sufficient elasticity to facilitate its outfitting by the wearer. In addition, the rubber sole portion affords adequate traction for use in most stream beds. A relatively thick gauge rubber construction is often required for protection against cutting, tearing, puncturing or flooding of the internal cavity.
Unfortunately, rubber waders are inherently heavy and cumbersome. The thicker gauge wader construction tends to reduce pliability and increase its bouyancy. The wader design and construction places constraints upon maneuverability, the ability to maintain balance within streams, and strains the physical endurance of the wader. Rubber waders are also subject to ozone deterioration. Such ozone exposure weakens the vulcanizate structure and particularly within the upper portions of the wader. These undesirable properties generally cause an ozone aged rubber wader to become less pliable and cracking or rupturing of its protective upper vulcanizate structure.
Within recent years, the art has attempted to overcome certain of these inherent deficiencies by the manufacture of wader products fabricated almost entirely from thermoplastic materials. The thermoplastic materials used in the upper wader construction generally comprises a thermoplastic composite material which includes one or more fibrous thermoplastic substrates in a woven mesh form, e.g. nylon, bonded together within a matrix of another thermoplastic substance such as polyvinylchloride (PVC). The upper wader portion may be appropriately cut from such calendered or laminated thermoplastic stock composite materials allowing for sufficient seaming margins to permit its overlapping and heat sealing together into the desired upper configuration. The thermoplastic bottom portions may be manufactured by conventional methods such as slush or injection molding techniques. The prefabricated thermoplastic uppers are typically heat sealed onto the thermoplastic bottom.
The major advantage of the thermoplastic wader products resides in its lightweight construction and ozone resistance attributes. Unfortunately, many of the other desirable attributes inherent to conventional rubber vulcanizate wader products, e.g. such as durability upon aging and use, resistance against cutting or puncture, elasticity, insulative value, comfort, permanency of the sealed regions against attrition or flooding, stream bed treading, etc., are sacrificed.
A long-felt need has existed for a lightweight wader product fitted with a rubber bottom and a lightweight thermoplastic upper securely and permanently bonded thereto. However, it is of paramount importance that such a proposed wader product afford protection against water penetration and flooding. A possible approach for securing vinyl uppers to rubber bottoms would involve simply sewing the vinyl uppers onto the rubber bottoms and sealing the stitchings with a waterproof sealant. Such an approach is not, of itself, a satisfactory solution to the problem. Perforations caused by stitching must not only be completely sealed but also must be able to permanently retain its sealant integrity. Stitching inherently fails to consistently produce a uniform bond between the stitched components and this factor becomes even more pronounced upon usage of the wader. Consequently the stitched and sealed area tends to fatigue and deteriorate with wear, which in turn, leads to leakage and flooding. Such matters are further compounded by acute manufacturing and quality control problems which make it especially difficult to consistently produce a water-tight wader on a mass production basis.
Several inherent bonding difficulties arise when one attempts to simply adhesively bond a wader vinyl upper directly onto a vulcanizate bottom. Direct adhesive bonding of a wader vinyl upper onto the rubber vulcanizate bottom is not feasible. Adhesive compositions compatible with rubber vulcanizates are generally incompatible with a thermoplastic upper. Although a rubber vulcanizate may be chemically treated to render it compatible to a thermoplastic adhesive composition, the normal use of the wader would place considerable strain and fatigue upon any such adhesive bond therebetween. Migration of chemicals deleterious to adhesive bonding reagents, e.g. plasticizers, from either the vulcanizate or thermoplastic upper may also destroy the efficacy of the adhesive bond. Elasticity differences also exist between the rubber vulcanizate and a thermoplastic upper. A wader is also subjected to repetitive stretching, relaxation and restretching of its structural components during its normal usage. The most vulnerable and critical point for preserving the desired water-tightness in such a proposed wader product exists within the joining bond between the vinyl upper and the vulcanizate. The bonding area must necessarily possess sufficient strength and durability to permanently maintain its structural integrity and water-tightness.